Adjustable resistance unit



` 4th and Elm streets,

except for convenience in UNITED STATES PATENT OFFICE.

BENJAMIN F. OLER, OF W'ODBURYA HEIGHTS, NEW

JERSEY.

ADJUSTABLE RESISTANCE UNIT.

I Specification of Letters Zlateiit.

Application led'September 28, 1918. Serial No. 256,054.

To all whom t wwyconcem:

Be it known that I, BENJAMIN F. OLER, a citizen of the United States, residing at Woodbury Heights, in the county of Gloucester and btate of New Jersey, have invented a certain new an useful Adjustable ,Resistance Unit, of which lthe following is a specification.

My `invention relates to resistance units which are used inv connection with electrical apparatus and are adjusted in position until an unknown required resistance is secured.

The purpose of my invention is to make the unit more compact at ythefsamie time that the short-,circuiting contact is' removed from possible injury an placed within the coil.

A Jfurther purpose is to provide a shortcircuiting contact which will llow up the movement of the resistance wire due A/toy ex pansion by reason of heat. s

Further purposes relate to the structure of the unit and will appean inthe specification and in the claims.

I have preferred to illustrate my invention by but one form,-selectingtherefor/a form which is simple, ineijrpensivelJ compact and eiiectivegand which'at the' same' time well illustratesitlre' principles'bf my invention. f

Figure' 1 is a sideelevation, showing my preferred form.

Figs. structure seen inFig. l.

Fig. 3 is a section Fig. 2 on linev 33.

Fig. 5 is a section of Fig. 3 upon line 575.

Fig. l6 is a diagrammatic view showing Hconnections made.

In the drawings, similar numerals indicate like parts.

In the type of resistance unit to which my inventionis applied, the unit must have a rangev covering t e required resistance, but,

preliminary setting of the adjustment, it is not necessary that the amount of the resistanceused be known at any time.

In carrying out my# invention, resistance wire an insulating core form. The mcore may I wind the desirably be made of porcelain and the usual material for the winding is German silver.

resistance is effected by cutting out coils ci the wire by means of a short-circuiting rider contact. As far as outlined the construction is well known and quite generally used.

, as at 14. The spool 2 and 4 areendzelevationsof the 10 within the grooves 11 of 12 of convenient spool- The variation inv` However, instead of ap l'ingthe rider. contact upon the outside ofthe spool winding, I slit the spool, as at 13, invordei to provide for an interior contact. In order to avoid unduly weakening the spool, I prefer not to slit it the entire length, but unite the porcelain across both ends of the slit,

is shown as conveniently open at one end at 15 and closed at the other end at 16 for support of an adjusting screw.

' The ends provide for convenient attachment of contact heads 18 and 19 which are in good electrical contact with thewire and may be alike except for the size of openings 20 and 2l in them. They are retained in position by crimping the edges 22 about `the beads. They may also protect and hold the ends of the wire. These contact ends may be made of any reasonably good conductor and The spoolis mounted upon 24 which are nearly alike.

Their openings 20', 2l are different and bracket 23 is flattened at the top at 25 and apertured at 26 for cooperation with a spring washer. The brackets are notched at 27, in the usual manner to fit over hinding posts.

Within the spool 12 is mounted an 'adjustingscrew 28 which is turned by a knurled andslotted head 29l and is held from longitudinal movement by the closed lend' of the spool. The reduced portion 30 Lof the screw is passed through the hole in thespoolfso brackets 23,

that the shoulder engages one side of the..

thereof.

head and a washer 3l, the other side The washer is held inposition by a pin 32. At the opposite end the shaft 33 of the screw fits within the openings of the ,head and standard and is supported by them. l.

In order that the screw may 'hare gopd electrical contact with the standard 23, a spring strip 3a is provided, which is effective as a washer and is retained against vrotation with the screw by the projections 35 and 36 engaging with the flattened top -o the standard and itting in the opening 26 thereof respectively. The hole 2O2 provides for passage of the screw through the strip. The screw makes contact chiefly with the washer. The standards and heads may bev of the spool are beaded at 17 to l are conveniently formed of phosphor bronze.

in good electrical contact with one end of the resistance wire, but is insulated from the end of the lscrew; also that the head 'sl'is in .good electrical contactvwith the opposite end of the wire and with the screw.

The short-circuiting contact with the wire is secured by a nut 37 advanced and retractedy by screw rotationl and a preferably v spiral spring contact finger 38 carried by the outwardly v nut and turned at 39 to extend through the recess or slot 13 into engagement' vwith the interior of the wire. The projection is outwardly spring-pressed in order that it may make good contact with the wire and follow up the wire as the latter expands,` by reason of the heat therein. At the same tune it engages with' the sides o .f the` slot 13jto prevent rotation of the nut.

In operation, the unit is placed within the circuit bymeans of the usual .binding posts and the knurled-head is turned to bring myself to this construction further than may be required by limitation of the scope of the claims through the ticularly true because I'know that there are many ways in which the construction ma differ from that described, some of whic I have myself designed.

aving thus described my invention, what I claim as new and desire to secure 'by Letters Patent is A y 1. A resistancev unit comprising a longitudinally slotted insulating spoolhaving lbeaded ends, a resistance wire wound thereon, electrically conducting spool ends turned over the beads and making contact with the wire at the two ends, connections for the ends and an adjustable contact device enprior art. This is'parcontact device to prevent it.

gaging the wire and electrically connected with one of the ends of the wire to short circuit; a part of the wire. l

2. In a resistance unit, an insulating spool having beads on the end, a wire'wrapped upon the spool, heads on the ends of. the spool turned over the vbeads and engaging and protecting the ends of the wire, a screw within the spool fixed against longitudinal movement by engagement with-one end of the spool and electrically connected with one of the headsv and acontact device carried by the screw and adapted to engage with the wire .to short-circuit part of the wire.

3. In a resistance unit, a longitudinally slotted insulating 'spool' having an, insulating headtherein,` a screw mounted therein and heldagainst longitudinal movement by .the insulating head, electrically conducting heads for the two ends of the spool, one supporting the .screw and the other insulated from it, an electrically conducting nut on said screw and an electr1callyconducting spring contactspiraled about the screw,'re

talning the nut agalnst' rotation and engaging thel resistance wire through 'the slot.

4. A lresistance unit comprlsng a longitudinally slotted spool, a resistance wire wound thereon, electrically conductingl heads secured to the .spool and electrically connecting withv the ends of the wire, electrically-conducting standards supportingthe spool and connecting it with the circuit with which the unit is to be used, a screw within v the spool secured a ainst longitudinal movement at one end t ereof, aspring contact device between the other endof the screw and its standard and means upon the spring with respect to the standard.-

' 5. In a resistance unit, a` longitudinally slotted spool, a wire wound thereon, connections -for the wire, connected with one end of the wire, a nut upon the screw and a spring contact spiraled about the screw connected with the nut to prevent rotation thereof and engaging the wire through the slot. BENJAMIN F. OLER.

from rotating a screw within the/spool.- 

